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Counting

Count outcomes without listing them. Build from the multiplication principle to sampling with and without replacement and the binomial coefficient, then decide which count a problem needs. Finish with arrangements of repeated objects and the binomial theorem.

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5

lessons

50

practice questions

12

prerequisite lessons

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Lesson 01 · The multiplication principle

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Click an outcome on the bottom row to follow its route.

Each of the 22 branches splits into 33, so the bottom row has 2×3=62 \times 3 = 6 outcomes.

The diagram from the lesson itself, running live.

5 of 8 lessons

5 lessons you can take today, and 3 more being written. Expand any one to see what it covers. Each unlocks when its own prerequisites are passed.

01

The multiplication principle

Preview

8 questions

Learn how to count the outcomes of a multi-stage choice by multiplying the number of options at each stage, and when that applies.

Covers

Counting sequential choices

When multiplication applies

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02

Sampling with replacement

12 questions

Learn how to count outcomes when objects look alike by labelling them, count ordered samples drawn with replacement, and count the subsets of a set.

Covers

Labelling objects

Sampling with replacement

Counting subsets

03

Sampling without replacement

12 questions

Learn how to count ordered samples drawn without replacement, count the arrangements of a set of objects, and decide whether a scenario is sampled with or without replacement.

Covers

Sampling without replacement

Permutations

With or without?

04

The binomial coefficient

12 questions

Learn how to count selections where order does not matter by counting in order and correcting for the overcount, and how to name and evaluate that count as the binomial coefficient.

Covers

Adjusting for overcounting

Counting groups of kk

The binomial coefficient

05

Choosing a counting model

6 questions

Learn how to choose the right way to count a selection of objects by asking whether an object can be drawn more than once and whether the outcome records the order of the draws.

Covers

The sampling table

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Properties of the binomial coefficient

In drafting

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Arrangements with repeated objects

In drafting

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The binomial theorem

In drafting

Where this unit sits in the curriculum

This unit is part of our Essential Probability & Statistics for ML learning path, which contains 23 lessons. Every one of them is drawn below.

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Every dot is a lesson and every line a prerequisite. The 5 red dots are the lessons in Counting; the 12 blue dots feeding into them are the lessons Counting depends on; the 6 pale dots are the rest of the learning path, which come after Counting or alongside it.CountingFirst lessons on the left23 lessons

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5 lessons in this unit

12 prerequisite lessons across the unit, counting every step back to the start

6 other lessons in the learning path - after this unit, or alongside it

Every dot is a lesson, every line a prerequisite. You can only start a lesson once you have mastered all of its prerequisites, so you are always building on solid foundations.

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